Condenser welding system



Dec. 55,1944. H, KLEMPERER CONDENSER WELDING SYSTEM Filed April 15, 1943 w Q A mR #5 P w-% M Patented Dec. 5, 1944 2,364,079 CONDENSER WELDING SYSTEM Hans Klemperer, Belmont, Mass., asslgnor to Raytheon Manufacturing Company, Newton, Mass, a corporation of Delaware Application April 15, 1943, Serial No. 483,149

(Cl. 320l) 9 Claims.

This invention relates to Welding systems in which the electrical energy. is stored in any suitable storage means, such as a condenser, for' subsequent discharge through a welding load circuit in order to deliver welding current to a resistance welding load.

In condenser welding systems using very high capacities (for example 4000 mid. or more) and correspondng high-turn ratios of the welding transformer (for example 600 to 1) the Welding circuit is aperiodic. Accordingly the voltage of the welding transformer does not reverse, under these conditions, but decays slowly without changing its polarity. The usual shunt circuit, commonly provided across the terminals of the primary wind'ng of the transformer, is ineffective in such aperiodic circuits since the shunt tube can only pick up" upon reversal of the condenser voltage.

These characteristics of aperiodic circuits result in the delay of the operation of such welding systems in two ways: (1) The opening of the electrodes has to be postponed until the transformer current has died out in order to avoid spitting. (2) The recharge of the condenser has to be' withheld for a very considerable time because the series tube remains ignited and therefore continues to be conductive until the long decay period of the transformer voltage has been completed. Q

It is an object of the present invention to overcome the above-mentioned defects of high capacity Welding systems and provide a system in which the decay current is terminated within a reasonable period of time thereby permitting the system to function at speeds of the same order as low capacity systems.

A further object of the invention is to provide a system n which the energy remaining in the welding circuit, at the moment of current interruption, is utilized to boost the residual condenser charge thereby reducing the line demand and also reducing the time required to charge the condenser.

The above and other objects and features or the invention will be apparent to one skilled in the art from a consideration of the following detailed description taken in conjunction with the accompanying drawing in which:

Fig. 1 is a diagram of the condenser welding system embodying this invention; and

Fig. 2 is a set of curves illustrating the mode of operation of the invention.

In the drawing, and referring first to Fig. 1 thereof, reference numeral I indicates a welding load to which welding current is to be supplied I from a secondary loop 2 of a welding transformer 3 having a primarywinding 4. The primary winding 4 is provided with end taps 5 and 6 and an intermediate tap l. The welding energy is adapted to be supplied to the primary winding 4 from a condenser 8 adapted to be charged from any suitable source of direct current, such as a rectifier, a direct current generator, or a battery. Impedances 9 and III, which are preferably inducta-nces, are provided between condenser 8 and the positive and negative terminals, re-v spectively, of the supply source. The positive side of the condenser 8 is connected to the intermediate tap l on the primary winding 4 and the negative side is connected to the end tap 5 of the primary winding 4 by way of a controlled ignition discharge tube ll. Tube H is preferably of the pool-cathode type having an anode l2 connected to the tap 5, and a pool type cathode i3 connected to the negative side of the condenser E and an ignite'r l4, which may be of any suitable type, but whichis preferably of the electrostatic type consisting of a conductor separated and insulated from the cathode by a thin layer of glass. The igniter i4 is adapted to be supplied with timed ignition impulses in a manner hereinafter mOre fully described.

A shunt c1 rcuit is provided between the anode l2 and the cathode 03 of the tube H, which circuit includes a rectifier tube l5 forming a snufier tube in series with a snumng condenser IS. The rectifier tube it may be of any suitable controlled type, but is preferably of the gas or vapor-filled type having a permanently energized cathode IT, a grid l8 and an anode 89. The cathode I! may be of the permanently energized thermionic filament, or other suitable type. The grid I8 is adapted to be supplied with timed snufiing impulses in a manner to be hereinafter more fully described. The anode i9 is connected to the positive pole of the snufilng condenser Hi. The snufllng condenser l6 may be supplied with direct current from any suitable source, such as a rectifier, direct current generator, or battery to which the condenser I6 is connected by positive and negative terminals 20 and 2|, respectively. Impedances 22'and 23, which are preferably inductances, are provided between the condenser l6 and the positive and negative terminals 20 and 2!, respectively.

A trailer tube 24, which is preferably of the same general type as series tube H, is provided with an anode 25 connected with the cathode l3 of series tube l l. A pool type cathode 26 of the tube 24 is connected to the end tap 8 of the primary winding 4. Since the anode 25 of tube 24 is connected to the cathode l3 of tube II and 26 and the igniter 21. It will be apparent that during periods when both the serie tube ii and the trailer tube 24 are conductive, a shunt circuit will be provided through these tubes between the two end taps 5 and 8 of the primary winding 4.

Ignition impulses for the igniter H are supplied from any suitable source and their timing may be controlled by the operator or by a suitable timing switch actuated automatically upon closure of the welding electrodes. This is shown diagrammatically by a push button switch ill, having an armature 32, adapted to close contacts 33 and at between the source of ignition impulses and the igniter M. Actuation of the push button switch 3i simultaneously actuates an armature 35 which closes contacts Elli and Si in a time delay relay circuit. The time delay relay functions to actuate an armature 5'38, a predetermined time after the closure of contacts 3t and 37!, and thereby closes contacts till. The contacts 39 and at are positioned in the circuit between the snufing impulse source and the grid is of the snufiing tube 115 to the end that snuillng impulses "from the source will be sup= plied to the grid it at a predetermined time after the ignition oi the series tube ii.

The operation of the system will be described in conjunction with the set of curves shown t Fig. 2, These curves do not purport to show the operation of the system quantitatively, although they do represent in a general qualitative inan ner the nature or" said operation. It will be ob= vlous that the curves apply to a system in which the capacity of the condenser bani: 8 and the turn-ratio of the transformer 3 is such that the system is aperiodic.

The condenser 8 is charged to the desired potential from a suitable source capable of impos ing' such potential during the period intervening between successive welds. An ignition impulse is supplied to the igniter it from any suitable source, it being understood that this igniting its= pulse is timed in accordance with the well-lrnown practice to occur after the electrodes have been applied with the desired pressure to the resist ance welding load l. Upon ignition of the series tube M by the igniter it, the condenser 8 discharges through that portion of the welding transformer between the taps l and 5. As shown in the set of curves shown in Fig. 2, at the instant, indicated as To, that the tub ii is ignited there is an abrupt increase in the transformer voltage indicated by the curve E followed by a gradual decay. The condenser voltage gradually decays along a similar curve Ec, while the welding current rises more gradually than the transformer voltage and decays still more gradually as indicated by the curve I. After a given time, as for example at the time T1, or after the voltage has declined to a given point, a. snufilng impulse is supplied to the grid it due to the closure of the contacts 39 and 40 by the armature 38 of the time delay relay. It will be understood that the time delay relay functions to close the snufllng impulse circuit atter a suflicient time has elapsed since the initiation of the discharge of condenser 8 to permit the current induced in the welding load to decay to a relatively low value, such as the relative value of the current indicated by the curve I at the time T1.

The polarity of the condenser I8 is such that, upon conduction of the tube I5, it applies 2. voltage to the tube H in a non-conducting direction and therefore extinguishes conduction in said tube. Accordingly the series tube II is snufied or extinguished by the energy received from snufllng the condenser [6. The discharge of the condenser 8 through the circuit provided by the upper portion of the primary winding 4 and the tube H is immediately terminated by the snufling of the series tube H. At this time, T1, a substantial amount of energy is still stored in the load circuit including the transformer 3 which energy tends to cause current to continue to flow through the primary 4 in the same direction as before. The current, resulting from the energy stored in the load circuit, acts in the same direction as the energy stored in the condenser 16. Thus upon the extinction of the tube H the current from the primary 4 of the welding transformer 3 is deflected into the snuifer circuit in a direction to reverse the polarity of the condenser it, that is to say, in the same direction in which this condenser tends to discharge through the tube 15, the trailer tube 24, and the primary 6 of the welding transformer 3. Thus the trailer tube 2 3, the anode 25 of which is connected to the cathode side of series tube l l, and accordingly to the cathode ll of the thyratron i5, is subjected to a considerable potential difference between its anode 25 and its cathode 26. Simultaneously an igniting impulse is supplied to the igniter 21 of trailer tube 2% byway of rectifier tube 28, the cathode 3b of which is connected to the igniter 2?. Thus the tube 24% is ignited and becomes conductive substantially immediately upon the snuiling 0:? the series tube ll. momentarily a shunt circuit exists between the two end taps '5 and b of the primary winding 4, which shunt circuit includes the snuffing condenser is, the thyratron l5, and the trailer tube 25. However, this shunt path is effective only until a counter voltage has been built up upon the condenser HE that is to say until the polarity of this condenser has reversed. 'Thereupon there is no ef- .tective shunt circuit between the two ends 5 and (3 of the primary winding t, but an effective circuit exists between the two poles of the condenser 8 by way of the trailer tube 24 and that portion of the primary winding between the end tap E and the intermediate tap i so that the 'energy of th load circuit is fed from the primary 5 by way of the intermediate tap l to the positive side of the condenser E, that is to say in the same direction as the charging current for this condenser. Accordingly there is an abrupt reversal of the transformer voltage at the point T1 while the condenser voltage begins to rise as shown by the portion of the curve Ec between the point T1 and T2. By the time T2 the transformer voltage Ep has returned to zero and the energy remainin in the transformer at the time T1, when .the series tube H was snuffed, has been returned to the condenser 8 as indicated by that portion of the'curve E0 between the time T1 and-T2.

Although there has been herein described but a single embodiment of the present invention other embodiments within the scope or the appended claims will be obvious to those skilled in the art from a consideration of the form shown.

What is claimed is:

1. An electrical system comprising a condenser, means for charging said condenser, a load circuit, means for discharging said condenser through said load circuit, means to terminate the flow of current from said condenser through said load circuit prior to the complete discharge of said condenser, and means to return the remaining energy of said load circuit back to said condenser in the same polarity as said charging means.

2. An electrical system comprising a condenser, means for charging said condenser, a load circuitincluding a transformer having a primary circuit including said condenser, said circuit being aperiodic, means in said circuit for controlling the discharge of said condenser, means effective prior to the complete discharge of said condenser for terminating the discharge thereof and returning the remaining energy of said load circuit back to said condenser in the same polarity as said charging means.

3. An electrical system comprising a condenser, means for charging said condenser, a load circuit including a transformer having a primary circuit connected with said condenser and a secondary circuit including a load, circuit controlling means for permitting the partial discharge of said condenser through at least a portion of said primary circuit, means to terminate said partial discharge and means to return the remaining energy of said load circuit back to said condenser in the same polarity as said charging means.

4. An electrical system comprising a condenser, means for charging said condenser, a load circuit including a transformer having a primary circuit connected with said condenser and a secondary circuit including a load, circuit controlling means for permitting the partial discharge of said condenser through a portion of said primary circuit, means to terminate said partial discharge and means to return the remaining energy of said load circuit back to said condenser in the same polarity as said charging means through another portion of said primary circuit.

5. An electrical system comprising a condenser, means for charging said condenser, a load circuit including a transformer having primary windings a portion of which are connected to opposite poles of said condenser and forming therewith an aperiodic circuit, means in said circuit for controlling the discharge of said condenser, means eflective prior to the complete discharge of said condenser for terminating the discharge thereof, and a second circuit including a second portion or said primary windings for returning the remaining energy 01 said load circuit back to said condenser in the same polarity as said charging means.

6. An electrical system comprising a condenser, means for charging said condenser, a load cir cuit including a transformer having a primary circuit including said condenser, said circuit being aperiodic, a controlled ignition discharge tube in said circuit for controlling the discharge of said condenser, means eiiective prior to the complete discharge of said condenser for snuiiing said tube and thereby terminating the discharge of said condenser, and means for returning the remaining energy of said load circuit back to said condenser in the same polarity as said charging means.

7. An electrical system comprising a condenser, means for charging said condenser, a load circuit including a transformer having a primary circuit including said condenser, said circuit being aperiodic, a controlled ignition discharge tube in said circuit for controlling the discharge of said condenser, means eiiective prior to the complete discharge of said condenser for snuffing said tube and thereby terminating the discharge of said condenser, and means including a second controlled ignition discharge tube for returning the remaining energy of said load circuit back to said condenser in the same polarity as said charging means.

8. An electrical system comprising a condenser, means for charging said condenser, a load circuit including a transformer having a primary circuit connected with said condenser and a secondary circuit including a load, an ignition controlled discharge tube in said primary circuit controlling the partial discharge of said condenser through a portion of said primary circuit, and means eifective after a predetermined time delay to snufi said tube and thereby terminate said partial discharge and return the remaining energy of said load circuit back to said condenser in the same polarity as said charging means.

9. An electrical system comprising a condenser, means to charge said condenser, a load circuit including a transformer having a primary circuit connected with said condenser and a secondary circuit including a load, an ignition controlled discharge tube in said primary circuit controlling the partial discharge of said condenser through a portion of said primary circuit, a shunt circuit including a snuifing condenser, means to charge said snufiing condenser, means connecting the positive pole of said snuffing condenser with the cathode of said ignition controlled discharge tube, said means including a controlled discharge tube timed to supply snuffing impulses from said snufling condenser to said first mentioned tube and thereby terminate said partial discharge and return the remaining energy of said load circuit back to said condenser in the same polarity as said charging means.

HANS KLEMPERER. 

